This invention relates to ladders and in particular to portable ladders.
Portable ladders usually comprise two side members, and interposed between the side members are located a plurality of conveniently spaced rungs. The number of rungs depends upon the length of the side members. Extending ladders comprise a number, generally two or three, of smaller ladders slidably disposed within the main ladder and capable of being secured to an upper rung of the main ladder. The side members of portable ladders are essentially parallel, although some portable single ladders may have converging or diverging side members, particularly at their upper ends. All these ladders are intended to rest at their lower end on the ground and at their upper end against a resting object. In this specification, the term xe2x80x9cgroundxe2x80x9d includes any solid surface on which ladder is generally used, such as, for example, compacted soil, lawn, concrete, paving, wood, and the like. In this specification, the term xe2x80x9cresting objectxe2x80x9d means the object against which the ladder rests such as for example, brickwork, roofing, guttering, scaffolding, tree, and the like.
The object of a ladder is to enable a workman to attain a greater working height. Such use is conventional and extends to the professional workman and the amateur user around the house.
Much damage can be caused to a resting object by inadvertent striking of the upper end of the ladder against the resting object when the ladder is being placed into position. For example, when a ladder is being positioned near a window for cleaning, the upper end of the ladder could break the window or damage the window frame; also for example, if a ladder is being used on a roof, slates or tiles, being the resting object, may be damaged if the ladder strikes the roof sharply when being positioned or manipulated on the roof. This is generally caused by the upper ends of the ladder being smacked against the resting object. Such damage may be very costly to make good, particularly if the windows, frames or roof are on an old building so that repair material is not readily available or unavailable.
There is therefore a need for an apparatus that can be used on ladders to enable the possibility of such damage to be eliminated or much reduced.
According to the present invention, an apparatus is provided for a portable ladder having essentially parallel side members which apparatus comprises having a pair of arms for attachment to the upper end of each side member of the ladder, at least one resilient roller mounted on a corresponding axle or axles located between and/or outwardly from the arms, means to locate each arm on each side member and means to secure the arms to the side member, the length of the roller being at least 50% of the distance between the arms.
The side members of conventional ladders often have an I or T shaped cross section, but preferably, principally for increased strength, have a rectangular or square box cross section. Such ladders are generally made from a light metal, such as for example, aluminium or aluminium alloy.
The arms of the apparatus of the present invention are conveniently made from similar metal, and have a cross section appropriate for attachment to the side member. Thus, where the side member has a square or rectangular cross section, the arms will have similar cross section, but larger or smaller dimension at the end of the arm to locate the arm on the side member so that that part of the arm may slide over or preferably within the side member. That end of the arm may be similarly adapted for location onto a side member having an I or T cross section. Because such location is slidable and the arm may disengage form the side member, means should be provided to secure the arm to the side member. The securing means should be releasable so that the apparatus of the invention can be removed from the ladder when not required. The securing means may be for example a bolt extending through both the arm and the side member, maintained in position by a nut or wing nut, but is preferably a spring catch, releasable when the apparatus is no longer required.
The arms should be essentially parallel, and may be straight or, preferably, arcuate. If arcuate, the ladder is then conveniently a short distance, typically about 15 cm to 50 cm, preferably 20 cm to 35 cm, from the resting surface so making work at or near the resting surface somewhat easier. By arcuate is meant that the arms progress through about 30xc2x0 to 150xc2x0, preferably 60xc2x0 to 120xc2x0, and most preferably essentially 90xc2x0 through sharp angle or angles, or preferably through a smooth curve, preferably an arc.
The roller is mounted on, and can rotate, about the axle. The axle is preferably mounted between the arms, but may extend also or only outwardly from the arms. The axle is conveniently a rod which is provided with means to allow replacement of the roller; for example if the axle is located between and through the arms, it may be provided with a head at one end to abut the outside of one arm and a screw thread and wing nut at the outer end of the other arm.
By the term xe2x80x9crollerxe2x80x9d herein is comprehended a plurality of such rollers mounted on the same axle.
The roller may be made from any suitable resilient material. It may be made for example from synthetic or natural rubber, from flexible thermoplastic such as for example plasticised polyvinyl chloride, or from such materials which are in the form of a foam. A preferred roller is made from a foam, which is, provided with a harder, but still flexible, skin. The skin may be provided with ridges and dimples on its surface. In a preferred embodiment the roller is replaceable; in a further preferred embodiment the resilient material is replaceable. The length of the roller, if located between the side members, should be at least 50%, preferably at least 75% but no more than about 95% of the distance between the side members so that the roller may freely rotate about the axle. If a roller is located, or rollers are located, outside the side members, then the total length of these rollers should be at least 50%, preferably at least 75% of the distance between the side members.
In a further embodiment of the present invention, the arms are pivotally located and latchably secured to the upper end of at least one side member. Therefore the roller can be pivoted into a desired position, relevant to the particular job required of the ladder, and releasably maintained in that position. On release of the latch, the roller can be pivoted back to a storage position alongside (that is underneath) the ladder but not proud of the upper end of the ladder; such a storage position facilitates use of the ladder when the roller is not required, but enables easy use of the roller when desired. The latching means could be, for example, a friction device or preferably a ratchet device located at or adjacent the pivot.
Therefore in operation, the ladder is being placed against, for example, a window ledge or a roof, the roller spreads the load of the ladder and enables the ladder to more easily manipulated into the desired position, and without damaging or with minimum damage to the resting object.